"Find the smallest common multiple of the provided parameters that can be evenly divided by both, as well as by all sequential numbers in the range between these parameters."

smallest-common-multiple.js

// Callback to calculate the Greatest Common Divisor,
//  used within the scm callback.
function gcd(a, b) {
  if (!b) {
      return a;
  }
  return gcd(b, a % b);
}

// Callback to calculate the Smallest Common Multiple,
//  used within the main program.
function scm(a, b) {
  return a * b / gcd(a,b);
}

// This is the crux of the biscuit:
function smallestCommons(arr) {
  var sortedArr = [], // Initialize some variables
      tmpArr = [],
      result = [];

  sortedArr = arr.sort(function(a, b) { // Define the sortedArr
    return a - b; // Sort ascending
  });
  
  for (i = 1; i <= (sortedArr[1] - sortedArr[0] + 1); i++) {
    tmpArr.push(i); // Generate tmpArr and prepare it for the result
  }

  result = tmpArr.reduce(function (a, b) {
    return scm(a, b); // Reduce the sortedArr using the scm callback
  });

  return result;
}

smallestCommons([1,5]);